When calling qmake like that, you are calling the qmake from your distribution, so if you don't want that you have to uninstall the corresponding packages.

Otherwise the simplest and more clean solution is to use the full path to the qmake version you'd like to use. That way you ensure that you are calling the exact version you want.

As for Qt Creator, if you are using your distribution's Qt Creator, then you have to add your Qt 5.8 to it in order to use it. Just go in the Settings under Build and Run, add your Qt 5.8 there and make a Kit using it.

Thanks for the reply. When used qmqke on Qupzilla, It returned an error message saying that Qupzilla needed qmake5.7 or above. Hence the qmake --version call. Is there a file that can be edited to turn off the Qt5 and allow the Qt5.8 to dominate?

If this is the wrong forum for this, please point me to the correct forum.